This invention relates to an ink jet recording apparatus comprising a head maintenance unit for maintaining the jetting characteristic of a recording head.
An ink jet recording apparatus comprises: a recording head mounted on a carriage reciprocating in a main scanning direction; and recording medium feeder for feeding a recording medium such as a recording sheet intermittently a predetermined amount in a subscanning direction at one time for jetting ink drops from the recording head to the opposed recording medium for recording while moving the recording head in the main scanning direction.
A monochrome ink jet recording apparatus normally is equipped with one recording head. A full-color ink jet recording apparatus is equipped with a black ink recording head for jetting black ink and color recording heads for jetting color inks of yellow, cyan, magenta, etc. Such a configuration is disclosed in Japanese Patent Publication No. 7-132615A, for example.
The principle of jetting ink from each recording head of the ink jet recording apparatus is as follows: As well known, ink is pressurized by a predetermined pressure in a pressure generating chamber and based on the pressure, ink is jetted as an ink drop of controlled size to the recording medium from each nozzle orifice in a nozzle formation face. Therefore, the ink jetting characteristic from each nozzle orifice of the recording head needs to be maintained constant and if the ink jetting characteristic varies, degradation of the record quality results.
The ink jetting characteristic of the recording head varies because of a rise in viscosity caused by evaporation and drying of ink in the nozzle orifices, ink hardening, clogging, deposition of dust, mixing of air bubbles, etc. Thus, the ink jet recording apparatus is provided with a head maintenance unit for excluding the variation causes of the ink jetting characteristic to maintain the ink jetting characteristic of the recording head constant for maintaining the jetting characteristic of the recording head.
First, the head maintenance unit comprises a capping unit. At the non-recording time, the capping unit seals the nozzle formation face for isolating the nozzle orifices from the outside, thereby suppressing drying of ink and arise in ink viscosity.
If the capping unit seals the nozzle formation face, clogging the nozzle orifices, mixing air bubbles into an ink flow passage, etc., cannot completely be prevented. Then; second the head maintenance unit comprises a suction pump capable of forcibly sucking and discharging ink from the nozzle orifices to remove clogging of the nozzle orifice and the mixed air bubbles. With the suction pump, negative pressure is made to act on the nozzle orifices in a state in which the capping unit seals the nozzle formation face, and ink is forcibly sucked and discharged from the nozzle orifices for removing the clogging, the mixed air bubbles, etc. Normally, the forcible ink sucking and discharging processing with the suction pump is executed when the record operation is restarted after the recorder halts for a long time or the user, who recognizes degradation of the record image quality, operates a dedicated switch on an operation panel.
If the forcible ink sucking and discharging processing with the suction pump is executed as described above, ink may be scattered and deposited on the nozzle formation face of the recording head and a meniscus of ink in each nozzle orifice is disordered. A foreign substance easily adheres to the nozzle orifices of the recording head over time. Then, third the head maintenance unit comprises a wiper for wiping the nozzle formation face as required.
The wiper has a plate-like wiping member made of a composite material comprising a wiping material made of an elastic plate of rubber, etc., on one side and a rubbing member having the same shape as the wiping material, made of felt, etc., on an opposite side and a holder for pinching and supporting the base end side of the wiping member. While the margin of the tip side of the wiping member is pressed elastically against the nozzle formation face, the wiping member is relatively reciprocated for cleaning the nozzle formation face. For example, the wiping material is pressed against the nozzle formation face at the forth or back motion time, and the rubbing material is pressed against the nozzle formation face at the back or forth motion time, thereby cleaning the nozzle formation face.
The cleaning operation with the wiping material of the wiping member is called xe2x80x9cwiping operation.xe2x80x9d The xe2x80x9cwiping operationxe2x80x9d takes an important role of uniforming, namely, stabilizing a meniscus of ink in each nozzle orifice in addition to wiping ink deposited on the nozzle formation face. Thus, the force of elastically pressing the margin of the wiping material against the nozzle formation face must be set to a soft and appropriate strength to such an extent that the meniscus can be stabilized reliably; this is a first technical demand.
The cleaning operation with the rubbing member of the wiper is called xe2x80x9crubbing operation.xe2x80x9d The xe2x80x9crubbing operationxe2x80x9d has a role of scraping off a foreign substance fixedly secured to the nozzle formation face. Thus, the force of pressing the margin of the rubbing material against the nozzle formation face must be set large to such an extent that the foreign substance fixedly secured to the nozzle formation face can be scraped off; this is a second technical demand.
However, hitherto, to meet the first and second technical demands for the wiper, a wiping member easily bent and a rubbing member harder to bend than the wiping member have been used only in combination. Thus, naturally there is a limit and both the technical demands are not easy to meet sufficiently.
It is therefore an object of the invention to provide an ink jet recording apparatus which has a head maintenance unit for maintaining the jetting characteristic of a recording head and can easily and sufficiently meet the first and second technical demands for the wiping member of the wiper, one of the head maintenance units.
To the end, according to a first aspect of the invention, there is provided an ink jet recording apparatus comprising:
a recording head; and
a wiping unit for wiping a nozzle formation face of the recording head including:
a slider reciprocally moving in a direction parallel with the nozzle formation face;
a wiper supported by the slider, one end of which is pressed against the nozzle formation face as a wiping operation when the slider moves in a first direction, while as a rubbing operation when the slider moves in a second direction opposed to the first direction;
a supporter for rotatably supporting the other end of the wiper on the slider;
a spring for urging the wiper toward the nozzle formation face while keeping an attitude of the wiper directed by a reaction force generated when the wiping operation is executed; and a rotation limitter for restricting the rotation of the wiper such that the wiper is rigidly supported by the slider when the rubbing operation is executed.
According to the configuration, during the wiping operation, the wiper is pressed against the nozzle formation face of the recording head using the elastic forces of both the wiper itself and the spring, so that the first technical demand that the wiper must be pressed against the nozzle formation face with a soft and appropriate strength to such an extent that a meniscus of ink in the nozzle orifice can be stabilized reliably as compared with the structure in the related art wherein the wiper is pressed by the elastic force of only the wiper itself can be met easily and sufficiently.
During the rubbing operation, the rotation limitter restricts rotation of the wiper for placing the wiper in a rigid support state, so that the wiper is strongly pressed against the nozzle formation face and thus the foreign substances fixedly secured to the nozzle formation face can be scraped off reliably; the second technical demand can be met easily and sufficiently.
Preferably, the wiper is composite member made of a wiping member which is an elastic plate and a rubbing member made of a material having a higher bending resistance than the wiping member.
According to the configuration, the wiping operation is performed with the wiping material appropriate for wiping and the rubbing operation is performed with the rubbing material appropriate for rubbing, so that the spring is also used, whereby the first and second technical demands can be met easily and sufficiently all the more.
Preferably, the wiping unit includes:
a holder for holding the other end of the wiper and rotatably supported by the slider through the supporter; and
an arm member one end of which supports the holder, and the other end of which is-engaged with the slider with a play of a predetermined stroke for absorbing the elastic force of the spring.
According to the configuration, the first technical demand can be met as a simple structures.
Preferably, the slider has a shaft member fitted into a slot formed at the other end of the arm member so as to be movable within the slot. The movable range of the shaft member corresponds to the play.
According to the configuration, the play of the predetermined stroke is provided in the movable range of the slot relative to the shaft body, namely, the spring action range is limited, so that the urging force of the spring can be used stably with a predetermined strength.
Preferably, the rotation limitter holds the wiper at one rotational limit position to execute the rubbing operation.
According to the configuration, when the wiper is at one rotational limit position, the rubbing operation is performed, so that the wiper cannot be rotated during the rubbing operation and thus a strong press strength can be provided according to a mechanically simple structure.
Preferably, the slider includes:
a main rack extending in a longitudinal direction of the slider; and
a pinion meshed with the main rack and rotating back and forth to reciprocally moving the slider.
According to the configuration, the slider is reciprocated by the rack-pinion mechanism, so that the stability of reciprocating the slider can be enhanced as a simple structure.
Preferably, the slider indudes a differential rack extending parallel with the main rack and having a first portion and a second portion. The pinion meshes both of the main rack and the differential rack in the first portion to move the slider cooperationally. The pinion meshes only the differential rack in the second portion to reciprocally tilting the wiper.
According to another aspect of the invention, the ink jet recording apparatus further indudes a differential rack being placed slidably in the longitudinal direction of the slider, wherein the differential rack is reciprocated in step with the main rack by rotating a pinion meshing with the differential rack in forward and backward directions and wherein at the move termination part of the slider in the forth motion direction, only the differential rack is further pushed out by the pinion and is moved in the forth motion direction, whereby the wiper is tilted in the forth motion direction.
Preferably, pitches of the main rack and the differential rack are substantially the same. The number of teeth of the differential rack is larger than the number of teeth of the main rack.
According to the configurations, the differential rack enables the wiper to be easily tilted in the forth motion direction after the termination of the wiping operation, whereby the wiper can be restored to the former position without bringing the wiper into contact with the nozzle formation face of the recording head after the termination of the wiping operation.
Preferably, the wiping unit includes:
a holder for holding the other end of the wiper and rotatably supported by the slider through the supporter; and
an arm member one end of which supports the holder, and the other end of which is engaged with the slider with a play of a predetermined stroke for absorbing the elastic force of the spring.
According to the configuration, the first technical demand can also be met as a simple structure in the structure using the differential rack.
Preferably, the slider has a member fitted into a slot formed at the other end of the arm member so as to be movable within the slot. The movable range of the shaft member corresponds to the play.
According to the configuration, the play of the predetermined stroke is also provided in the movable range of the slot relative to the shaft body in the structure using the differential rack, so that the urging force of the spring can be used stably.
Preferably, the rotation limitter is established by meshing the pinion with the differential rack.
According to the configuration, the differential rack and the main rack are moved in one piece by the pinion in the state in which the pinion, the differential rack, and the main rack mesh with each other at the same time, so that the wiper is restricted in rotation in the forth motion direction. Therefore, the strong press strength during the rubbing operation can also be provided as a simple structure in the structure using the differential rack.
Preferably, the ink jet recording apparatus further comprises an ink remover for removing ink adhered onto the wiper after the wiping operation has been executed. A front face of the ink remover is formed such that the wiper is brought into contact therewith gradually when the slider is moved toward the first direction. A rear face of the ink remover is formed such that a force for elastically bending the wiper applied by the front face is released and thereby the wiper is restored rapidly.
According to the configuration, ink is removed from the wiper by the ink remover, so that the capability of the wiper can be easily recovered. Preferably, the recovery operation is performed for each wiping operation. Since the ink remover has the front of the shape to allow the wiper to gradually start to come in contact with, splashing of ink can be decreased if the wiper with ink strikes the ink remover. Further, the ink remover has the rear of the shape to allow the wiper to be detached in a stroke after the wiper is bent in an opposite direction to the move direction as it is pressed against the front of the ink remover, so that ink can be splashed from the wiper at the instant at which the wiper is detached, and the capability of the wiper can be recovered reliably.
The front shape of the ink remover may be a slope, a face having a large number of asperities, a face formed with an opening at a position opposed to the end margin of the wiper, etc., for example.
Preferably, the ink jet recording apparatus further comprises an ink absorber for receiving ink removed and splashed from the wiper by the ink remover.
According to the configuration, the ink splashed instantaneously from the wiper can be reliably caught without being leaked to other parts.
Preferably, the ink jet recording apparatus further comprises:
a capping unit having a capping state in which the capping unit moves toward the recording head to seal the nozzle formation face and a non-capping state in which the capping unit moves away from the recording head to release the sealing of the nozzle formation face; and
a unit frame for retaining the wiping unit and the capping unit.
The wiping unit reciprocally moves in a space defined between the recording head and the capping unit in the non-capping state.
According to the configuration, the wiper is reciprocated in the space in the non-capping state of the capping unit, so that the recorder can be made compact.
Preferably, the ink jet recording apparatus further comprises:
a cap drive cam for changing a rotational movement thereof into the reciprocal movement of the capping unit between the capping state and the non-capping state;
a main rack extending in a longitudinal direction of the slider;
a pinion meshed with the main rack and rotating back and forth to reciprocally moving the wiping unit;
a drive gear meshed with the pinion to rotate the same; and
a shaft member for coaxially supporting the cap drive cam and the drive gear such that the reciprocal movements of the capping unit and the wiping unit are conducted at a predetermined timing.
According to the configuration, the drive gear for meshing with the pinion and rotating the pinion and the cap drive cam are placed on one support shaft member for timing reciprocal movement of the wiper and the capping unit, so that control can be simplified.
Preferably, the ink jet recording apparatus further comprises:
a subframe engaged with a part of the unit frame in a cantilevered manner; and
a cam follower, which is to be abutted against the cap drive cam, attached to the subframe.
The capping unit is disposed in a free end side of the subframe.
According to the configuration, the reciprocal movement of the capping unit can be performed by simple cam control.
Preferably, ink jet recording apparatus further comprises a valve drive cam supported by the shaft member coaxially with the drive gear and the cap drive cam. The capping unit includes:
a valve member for opening and dosing an internal space of the capping unit; and
an operator for operating the open/close state of the valve member, which is operated by the valve drive cam.
According to the configuration, the valve member for opening and closing the internal space of the capping unit can be opened and closed as a simple structure by simple cam control.
Preferably, ink jet recording apparatus further comprises a suction pump for applying negative pressure in the internal space of the capping unit, and provided in the unit frame to constitute a head cleaning unit together with the wiping unit and the capping unit.
According to the configuration, the suction pump, the wiper, and the capping unit make up the head cleaning unit in one piece, so that the head cleaning unit can be made compact and can be easily assembled.
Preferably, the wiping unit includes a plurality of units arranged parallel with each other, each composed of a pair of slider and a wiper. The recording apparatus further comprises a selector for selecting one out of all available combinations of the wiping units to be driven.
According to the configuration, the ink jet recording apparatus comprises the selector capable of selecting the wiping units to be driven, so that both or either of the wiping operation and the rubbing operation can be executed only for the nozzle array requiring both or either of the wiping operation and the rubbing operation; the efficient operation with no waste can be performed.
Preferably, the ink jet recording apparatus further comprises a select cam supported by the shaft member coaxially with the drive gear, the cap drive cam and the valve drive cam. The selector is cooperated with the select cam to execute the selecting operation when the select cam is moved in a first direction which is opposed to a second direction in which the cap drive cam and the valve drive cam operates the capping member and the valve member respectively. The shaft member is rotated in the second direction after the selecting operation has been conducted to drive the selected wiping unit.
According to the configuration, selecting a wiping unit and both or either of the wiping operation and the rubbing operation of the selected wiping unit can be easily accomplished by backward and forward rotating one cam support shaft.
Preferably, the moving direction of the slider is parallel with an extending direction of an nozzle array on the nozzle formation face.
According to the configuration, the wiper is moved in the subscanning direction rather than in the main scanning direction, so that it is less feared that ink may be scattered in the main scanning direction accompanying the wiping operation, and even with a recording apparatus adopting a multicolor head, it is less feared that color inks may be mixed by performing the wiping operation.
Preferably, the ink jet recording apparatus further comprises a passage through which a recording medium is transported to be subjected to the recording by the recording head, the passage extending obliquely from a top part of the apparatus to a bottom part of the apparatus. The moving direction of the slider is parallel with the passage and the first direction directs toward the end of the passage.